Communication nodes, which act as junction points for communication signals transferred between a plurality of sources, are required to handle a variety of popular communication protocols, such as Integrated Services Digital Network (ISDN) protocol, Asynchronous Transfer Mode (ATM), and Internet Protocol (IP). ISDN, an early attempt at a multi-service architecture (i.e., an architecture capable of handling a variety of communication encapsulations), which is based on the telephone hierarchy, apportions bandwidth in 64 kilobits per second (Kbps) circuits. With local area networks (LANs) operating at 10 megabits per second (Mbps), ISDN has proved too slow. ATM is a packet switching protocol that was conceived as a transport mechanism for broadband ISDN. ATM transfers information in fixed-length packets called cells. The cells travel over virtual connections (VCs) between communication nodes that are established prior to each communication session. The combination of fixed cell formats and VCs renders ATM a faster alternative to ISDN. Additionally, ATM handles bursts of data traffic more efficiently than time division multiplexing (TDM) and provides high-quality voice and video support.
The popularity of the World Wide Web (WWW) has encouraged the use of IP. As a result, low-cost, distance-insensitive IP-based transport has become an attractive alternative to leased lines and frame relay (FR). Additionally, Internet Service Providers (ISPs) have become serious contenders for enterprise traffic.
Unfortunately, all of the information transfer protocols have drawbacks. Specifically, ISDN provides a relatively low-speed access solution. ATM supports frame relay, virtual private networks (VPNs), circuit emulation, private branch exchange (PBX) interconnects and quality of service (QoS), but does not mesh easily with existing data protocols. IP supports applications such as Internet Access and VPNs, for which cost connectivity is important. However, IP has yet to demonstrate industrial-strength reliability. As a result, full service providers find it necessary to maintain parallel switching networks. Because such parallel networks require maintenance and service of a variety of devices such as, voice switches, frame relay switches, ATM switches, routers, add/drop multiplexers, and digital cross-connects, they have a high associated capital equipment cost.
Conventional communication nodes also have a variety of drawbacks. For example, conventional communication nodes fail to provide sufficient ease of scalability. Typically, conventional switching nodes provide a switching/routing network having a fixed bandwidth. However, as enterprises grow, their needs also grow. But, the fixed bandwidth switching routing network of conventional technology requires enterprises to predict such growth and purchase systems having sufficiently large bandwidth up front; thereby compounding the challenge of maintaining parallel networks. Another drawback of conventional systems is reliability. Because conventional systems fail to provide a single switch/routing network that can operate on a variety of protocols, today's Giga Points-of-Presence (GigaPoPs) and Access PoPs are a complex and expensive aggregation of core routers connecting smaller Access PoPs to the core transport capacity. These structures are fragile, with frequent service outages due to performance limitations and equipment failures. Enterprises cannot afford to be exposed to significant down time due to failures or updates associated with conventional technology.
Because the switching/routing networks of conventional systems are typically designed to operate under the constraints of a particular protocol, they lack the flexibility to adapt to emerging technologies, employing new communication protocols. As discussed above, different protocols provide different QoS features. Thus, another drawback of a network operating under the constraints of a single protocol is that a service provider cannot offer varying grades of service to users having differing priority requirements; thus causing service providers to forego a potentially significant source of revenue.